U.S. patent application number 15/786076 was filed with the patent office on 2019-04-18 for mitigation of print banding using a single user-controllable parameter.
The applicant listed for this patent is XEROX CORPORATION. Invention is credited to NASSER ALAVIZADEH, BRIAN J. DANIELS, DOUGLAS DEAN DARLING, REID W. GUNNELL, WALTER SEAN HARRIS, ERIC HYDE, ROBERT MARK JACOBS, LISA M. SCHMIDT.
Application Number | 20190114517 15/786076 |
Document ID | / |
Family ID | 66097570 |
Filed Date | 2019-04-18 |
United States Patent
Application |
20190114517 |
Kind Code |
A1 |
DARLING; DOUGLAS DEAN ; et
al. |
April 18, 2019 |
MITIGATION OF PRINT BANDING USING A SINGLE USER-CONTROLLABLE
PARAMETER
Abstract
A method of correcting print banding in a printer, including
initiating the banding correction process, generating prints with
various levels of banding based on different levels of voltages
applied to the array of jets, receiving an input from the user
selecting the preferred print, and adjusting voltage levels applied
to jets corresponding to the preferred print.
Inventors: |
DARLING; DOUGLAS DEAN;
(PORTLAND, OR) ; HYDE; ERIC; (PORTLAND, OR)
; HARRIS; WALTER SEAN; (PORTLAND, OR) ; DANIELS;
BRIAN J.; (LAKE OSWEGO, OR) ; GUNNELL; REID W.;
(WILSONVILLE, OR) ; ALAVIZADEH; NASSER; (TIGARD,
OR) ; SCHMIDT; LISA M.; (PORTLAND, OR) ;
JACOBS; ROBERT MARK; (TIGARD, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XEROX CORPORATION |
Norwalk |
CT |
US |
|
|
Family ID: |
66097570 |
Appl. No.: |
15/786076 |
Filed: |
October 17, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06K 15/1219 20130101;
B41J 29/393 20130101 |
International
Class: |
G06K 15/12 20060101
G06K015/12; B41J 29/393 20060101 B41J029/393 |
Claims
1. A method of correcting banding in a printer, comprising:
initiating banding correction; generating a series of prints, each
print having a different level of banding, wherein the different
levels of banding correspond to different levels of voltages
applied to an array of jets; receiving an input from a user
selecting a print; selecting a banding parameter corresponding to
the selected print; and adjusting voltage levels applied to the
jets to account for the banding parameter.
2. The method of claim 1, wherein initiating banding correction
comprises receiving a user input to initiate banding
correction.
3. The method of claim 1, wherein initiating banding correction
comprises: generating a print; scanning the print for intensity;
and identifying a banding artifact.
4. The method of claim 1, wherein the different levels of voltage
correspond to discrete voltage levels.
5. The method of claim 1, wherein the series of prints represent
voltage levels both higher and lower than a current voltage.
6. The method of claim 1, wherein the series of prints include
prints at different dither percentages of a single color.
7. The method of claim 1, wherein the series of prints include
prints at different dither percentages of multiple colors.
8. The method of claim 1, wherein the method is repeatable as
needed.
9. A printer, comprising: a controller to send signals; a printhead
to receive signals from the controller and to produce prints based
upon those signals; a memory to store normalization data for jets
in the printhead, wherein the controller adjusts the signals sent
to each jet of the printhead based upon the normalization data; a
user interface to allow a user to communicate with the controller,
wherein at least one of the communications is a signal to start a
banding correction process, wherein the banding process causes the
controller to execute code to: adjust the normalization data for
jets in the printhead to produce multiple set of adjusted data;
send the adjusted data to the printhead; produce a print for each
set of the adjusted data; send a query to the user interface to
allow the user to select a desired print; altering the
normalization data to match the adjusted data corresponding to the
desired print; and storing the altered data.
10. The printer of claim 9, wherein the controller comprises one of
a microcontroller, processor, ASIC, or logic circuitry.
11. The printer of claim 9, wherein the different levels of voltage
correspond to discrete voltage levels.
12. The printer of claim 9, wherein the print for each set of the
adjusted data represents voltage levels both higher and lower than
a current voltage.
13. The printer of claim 9, wherein the print for each set of the
adjusted data represents different dither percentages of a single
color.
14. The printer of claim 9, wherein the print for each set of the
adjusted data includes prints at different dither percentages of
multiple colors.
Description
TECHNICAL FIELD
[0001] This disclosure relates to printing systems, more
particularly to printing systems that adjust for banding
artifacts.
BACKGROUND
[0002] Ink jet printers typically have intensity variations. These
may result from variations in the manufacturing process, the
assembly of the printhead, or other factors like operating
parameters. During manufacture, a normalization process typically
mitigates the variations by adjusting the operating parameters to
proactively account for the variations. Customer prints generated
after initial installation will typically not have banding
artifacts.
[0003] Once the printer operates in the field, it may develop
banding, an artifact in which the intensity variations form
noticeable bands across the printed image. This may occur because
individual inkjets in the array of jets do not age at the same
rate. The artifacts may reach a point where they become
objectionable to the customer.
[0004] A previous solution to this involves adjusting spatial tone
reproduction (or response) curves (TRCs). A TRC maps a desired
output value to the actual print values generated by the ink jet
printhead. Adjusting the TRC map can be an effective way to
compensate for banding that develops during the life of a
printhead. However, to use a TRC map to mitigate banding that
changes over the life of a printhead, the customer's system must
have the ability to scan images to measure intensity on a jet by
jet basis. There is a need for a process to correct for banding in
systems which do not have the ability to scan and measure
individual jet intensity.
SUMMARY
[0005] A first embodiment is a printer having a controller to send
signals to a printhead, a printhead to receive signals from the
controller and to produce prints based upon those signals, a memory
to store normalization data for jets in the printhead, wherein the
controller adjusts the signals sent to each jet of the printhead
based upon the normalization data, a user interface to allow a user
to communicate with the controller, wherein at least one of the
communications is a signal to start a banding correction process,
wherein the banding process causes the controller to execute code
to: adjust the normalization data for jets in the printhead to
produce multiple set of adjusted data; send the adjusted data to
the printhead; produce a print for each set of the adjusted data;
send a query to the user interface to allow the user to select a
desired print; altering the normalization data to match the
adjusted data corresponding to the desired print; and storing the
altered data.
[0006] A method of correcting banding in a printer includes
initiating banding correction, generating a series of prints, each
print having a different level of banding, wherein the different
levels of banding correspond to different levels of voltages
applied to an array of jets, receiving an input from a user
selecting a print, selecting a banding parameter corresponding to
the selected print, and adjusting voltage levels applied to the
jets to account for the banding parameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 shows an embodiment of a jet normalization.
[0008] FIG. 2 shows an illustration of intensity variations that
develop over life.
[0009] FIG. 3 illustrates intensity variation reduced to its
smallest repeating pattern.
[0010] FIG. 4 shows an embodiment of a print system.
[0011] FIG. 5 shows a flowchart of an embodiment of a banding
correction process.
[0012] FIG. 6 shows a graph of adjustments based upon column
locations of jets.
[0013] FIG. 7 shows examples of banding prints in a minus direction
from a starting position.
[0014] FIG. 8 shows examples of banding prints in a positive
direction from a starting position.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0015] As used here, the term "printer" generally refers to an
apparatus that applies an ink to print media and can encompass any
apparatus, such as a digital copier, book-making machine, facsimile
machine, multi-function machine, etc., which performs a print
outputting function for any purpose. "Print media" or "substrate"
can be a physical sheet of paper, plastic, or other suitable
physical substrate suitable for receiving ink images, whether
precut or web fed. As used in this document, "ink" refers to a
colorant that is liquid when applied to an image receiving member.
For example, ink can be aqueous ink, ink emulsions, melted phase
change ink, or gel ink that has been heated to a temperature that
enables the ink to be liquid for application or ejection onto an
image receiving member and then return to a gelatinous state. A
printer can include a variety of other components, such as
finishers, paper feeders, and the like, and can be embodied as a
copier, printer, or a multifunction machine. An image generally
includes information in electronic form, which is to be rendered on
print media by a marking engine and can include text, graphics,
pictures, and the like.
[0016] The term "printhead" as used herein refers to a component in
the printer that is configured to eject ink drops onto the image
receiving member. A typical printhead includes a plurality of ink
ejectors, or inkjets, that are configured to eject ink drops of one
or more ink colors onto the image receiving member. The ink
ejectors are arranged in an array of one or more rows and columns.
In some embodiments, the ink ejectors are arranged in staggered
diagonal rows across a face of the print head. Various printer
embodiments include one or more printheads that form ink images on
the image receiving member. Some printer embodiments include a
plurality of printheads arranged in a print zone. Print media moves
past the printheads in a process direction through the print zone.
An individual jet in a printhead ejects ink drops that form a line,
or pattern, extending in the process direction as the image
receiving surface moves past the print head in the process
direction. The plurality inkjets, or jets, in the printhead are
used to make patterns in a cross-process direction, which is
perpendicular to the process direction across the image receiving
member.
[0017] The printhead receives control signals from a controller
that determines which jets deposit ink and which ones do not. The
term "controller" as used here means any controller,
microcontroller, processor, application specific integrated circuit
(ASIC), or logic circuitry that can execute programmable
instructions to control operation of the print head. The signals to
the print head generally take the form of voltages. The voltages
stimulate actuators to cause a jet to eject a drop of ink, or may
only partially stimulate an actuator to cause the ink in a jet to
move but not eject. The embodiments here only address the voltages
that stimulate an actuator to cause the jet to eject ink. The
controller also applies the jet normalization values to each jet as
required to achieve uniform drop volume and velocity.
[0018] During manufacture of a print system, the print head
typically undergoes a normalization process to adjust the voltage
waveform for each jet. The normalization process compensates for
manufacturing variations between printheads and jet-jet variation
within the printhead. FIG. 1 illustrates an example driving
waveform for an inkjet. In this embodiment, first the overall, or
"rail," voltage 300 is set for the voltage driving waveform in the
printhead to set the correct overall drop volume of the printhead.
Then, individual jets are given normalization values to compensate
for jet-jet variation. The normalization value determines where the
waveform will be truncated at 302 for a given inkjet. Individual
jets are tested at various normalization, or "norm" values 304 to
determine what level causes the jet to fire with the best velocity
and drop volume. In one embodiment 64 normalization values are
used. The normalization process then stores the rail voltage and
normalization values for each jet in a memory in the print
system.
[0019] Over time, the jets age. Not all jets age at the same rate.
FIG. 2 illustrates an example of non-uniform aging. As shipped
there will be no significant variation in intensity across the
print, since the printhead was just normalized. Variations in aging
typically have both a random and a systemic component. The random
component does not typically result in noticeable artifacts to the
consumer. The systemic component can result in artifacts that are
noticeable to the customer. The systemic component may correlate to
the system architecture or arrangement and may result in an
artifact called banding, where the intensity variations form bands
within the printed image.
[0020] FIG. 3 shows one example of a banding in printhead, where
the controller connects to the printhead by flexible cables, or
"flex cables." The columns of jets that reside to the outer edges
of the flex cables tend to age faster than those near the center of
the flex cables. In that example the banding correlates to the
column position within each flex cable, and the pattern is repeated
across the printhead for each flex cable. In another example, the
aging rate may be different for jets near the upper or lower edges
of the array of jets. In yet another example, aging may be
different for jets depending on their location within the internal
fluidic manifold structure. The differences in aging may result in
banding that correlates with the geometry of the printhead in a
predictable manner.
[0021] The repeatable banding signature for a particular printhead
design may be determined by inspection and analysis of the geometry
or by empirical testing of multiple printheads with the same
design, or both. In the embodiment described above, the signature
was a repeating pattern. But, in other embodiments, the banding
signature may not be repeating, as in the case of a printhead that
is controlled by one large flex cable, rather than several discrete
flex cables. Once the repeatable signature is determined, the print
system can use that knowledge to compensate for banding.
[0022] FIG. 4 shows an embodiment of a print system 10. The print
system has a printhead 12 with an array of jets to deposit ink on
print media or substrate 14. The printhead 12 responds to signals
from the controller 16 to deposit ink on the substrate or not. The
print head receives ink from a supply 22.
[0023] In the embodiments shown here, a user or consumer detects
the banding artifact and uses a user interface 20 to begin the
banding correction process. The user interface may consist of a
display screen and some sort of user input device, such as buttons
or a touch screen. For example, the print system may have a way to
allow users to select print options, etc., through the user
interface.
[0024] The print system of the embodiments here includes a memory
18. The memory may store instructions to be executed by the
processor, as well as information regarding other print parameters
such a paper size, resolution, color selection, etc. In addition,
the memory will include the normalization values discussed earlier,
as well as other data used to generate prints demonstrating
different banding parameter settings.
[0025] FIG. 5 shows an embodiment of a banding correction process.
Once a user has noticed banding artifacts, the user can employ the
user interface to start a banding correction process at 24.
Typically, user systems may not have the ability to scan an image
to detect banding artifacts. However, if the system does have such
a capability, the user interface may not be needed to start the
banding correction process.
[0026] In response to either the user input or the system automatic
start, the controller generates a series of print data sets, each
corresponding to a different banding parameter at 26. The user then
reviews the prints and selects a desired print that has the lowest
noticeable banding at 28. The system then adjusts the values in the
normalization data to account for the new banding parameter at 30.
This process may be repeated as often as needed.
[0027] FIG. 6 shows an example of the pattern for norm value
adjustments. The pattern for norm value adjustments match the
predictable pattern of banding that was determined as described
above. FIG. 6 is a continuation of the example where banding
correlated to the column position of the jets within the flex
cable. As the banding parameter is changed, the pattern stays the
same, but the magnitude is scaled by the value of the banding
parameter. The scaling factor, or banding parameter, can be either
positive or negative or zero. In this embodiment, the normalization
values were restricted to be integers. In other embodiments,
decimal values could be used, depending on the process for
normalization. In the embodiment shown in FIG. 6, the outer columns
on both sides of the flex cables are adjusted by the banding
parameter. FIG. 6 shows the pattern for norm value adjustments for
Banding Parameters (BP) of -10, -5, -3, 0, and, +3.
[0028] As the banding correction process proceeds, a set of prints
is made for various levels of the Banding Parameter. For each value
of Banding Parameter, the corresponding normalization adjustment is
determined for each jet. Then a print is made using normalization
values for each jet by adding the adjustment to the original
normalization value of that jet. FIGS. 7 and 8 show the resulting
prints based upon different Banding Parameters adjustments. FIG. 7
shows resulting prints starting at 0 adjustments and negative
values of banding parameter. FIG. 7 shows a range of Banding
Parameters from 0 to -10. FIG. 8 shows resulting prints from
positive Banding Parameters in the range from 0 to +5. In this
example, BP=0 is the state of the printer at the start of the
process. After making prints at various levels of Banding
Parameters, the user can examine the prints and select the Banding
Parameter that results in prints with the least banding. In the
example shown in FIGS. 7 and 8, positive values of BP made banding
worse, negative values of BP reduced banding until BP=-4, beyond
BP=-4, banding became worse again. The least banding was achieved
at BP=-4. After the user determines the preferred value of BP, the
user inputs that preferred value of Banding Parameter into the
print system, and the system will store and use new normalization
values for each jet, based on that value of Banding Parameter, for
all prints going forward.
[0029] In this manner, a user can perform a banding correction
without any need for intensity scanning or technical expertise. The
print system can adjust for banding as often as needed to ensure
that users can make clean prints. In addition, the process may be
performed on one color at different dithering percentages, or with
multiple print sets for each color at different dithering
levels.
[0030] It will be appreciated that variants of the above-disclosed
and other features and functions, or alternatives thereof, may be
combined into many other different systems or applications. Various
presently unforeseen or unanticipated alternatives, modifications,
variations, or improvements therein may be subsequently made by
those skilled in the art which are also intended to be encompassed
by the following claims.
* * * * *